Structural Query Language
SQL in full Structural Query Language is a computer language used to manage databases. It is a language used in the management of database systems that was first developed in 1986 that could be used to dynamically query and display data in a better way to make its use and understanding easy by the users. SQL was developed from relational database which come in a series of interlinked data. Ever since its first development it has been severally modified changes that have been approved by both ISO and ANSI. The scope SQL covers includes insertion of data, the querying of the same data, its subsequent updating and general data control. The objectives of the above scope are achieved using the three major parts of SQL or languages are; Data Definition Language (DDL), a Database Manipulation Language (DML) and Database Control Language (DCL). @font-face { font-family: "Calibri"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0in 0in 10pt; line-height: 115%; font-size: 11pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; } Developing SQL commands may speed up the database sped and increase capacity by making new command such as SELECALL which select all tables. This will reduce command line in searching in too many tables. Also adding a compiler function which will have all the command stored into this function and correct the right syntax for all commands similar to the code correcting function when writing codes in C#. This will save time for the database programmer not to inspect every line of command and add more reliable search and update of the database. Another feature will help editing and developing the SQL command process is the copy paste feature that allow the programmer to copy and paste command lines within the SQL environment and highlight the mistakes that have typing error and provide suggestions to correct some mistakes and add undo function to undo the last 10 commands updates similar to the Microsoft office editing features. Also, adding a new function that provide a list of all commands in each session as a summary to give the programmer an extra review of the updating and programming process that was done in the session. This will make it easier to follow the editing and updating process and discover duplicate and wrong updates. The four major commands used in DML are: SELECT; which is used to highlight or display certain rows of the database that the user wants to work with, the UPDATE command which is used to effect any changes in the database. Taking as an example if we had, UPDATE student SET class='Five' WHERE class='Four' and mark >= 70. Will change all the records in the student table where the class field equal ‘Four’ and the mark field is greater or equal to 70. The DELETE command is used to delete all the selected data from the database. Having a commands like; DELETE FROM student WHERE mark < 60. This command will delete all the records from the student table where the mark is less than 60. . The INSERT INTO command is used to insert data into the database. INSERT INTO library set book name='Learning MySQL', author='plus2net group'. This command will insert a book named Learning MySQL with the author plus2netgroup into the library set table. With these four commands you can control or manipulate the data in a database. These commands contribute to the DML portion of SQL being the most widely used mostly in its ability to enable the modification of data at the time it is being put in and also in its retrieval and removal from the database. This makes it the ideal user interface in the SQL as through this the user is able to select and retrieve the data he wants. Mostly DDL deals with the deletion and creation of tables with its major commands being responsible for the creation and subsequent manipulation of tables in databases. These commands are; CREATE TABLE, CREATE INDEX, DROP TABLE and DROP INDEX. when one wants to drop a table from the database he uses the DROP TABLE command to do it alongside all records associated with it. On the other hand the CREATE INDEX command is used to create indexes to make searching the database faster it’s like looking in a index of a book. The generic syntax is CREATE INDEX "INDEX_NAME" ON "TABLE_NAME" (COLUMN_NAME). DROP INDEX does exactly what it sounds like it will drop the index you made from the database. With DDL you can create and destroy databases and their objects. The DCL is the third part of the SQL structure. This portion of the structure helps to control all the data and integrity within the database. DCL grants the ability to create primary, secondary, and other keys in the database tables. Another aspect of the DCL portion is the ability to control the data that is being manipulated within a table. With one of the most important features being the rollback command to restore data that was removed before the changes were made permanent.